Bacteriocins of indigenous clinical staphylococci: screening and charcterization

ABSTRACT

Staphylococcin [a class of bacteriocin] production was studied in 250 clinical isolates of staphylococci. 7% of the isolates exhibited intra - isolate and broad - range antagonistic activity. Crude bacteriocin preparations were not inactivated after prolonged thermal exposure [80°C] and were stable in the pH range of 5.4 - 10. The preparations also resisted the action of trypsin [a proteolytic enzyme], lysozyme [a glycolytic enzyme] and lipase [a lipolytic enzyme]. However, one of the extracts [Staphylococcin AB201] was sensitive to heat and trypsin. All the preparations retained their bioactivity after prolonged [16 weeks] refrigeration and freezing. Attempts to induce bacteriocin production [with UV, 0.5% mannitol and 2% yeast extract] and to elute cell bound bacteriocin [with 0.1M, 1M and 5M NaCl and 0.05M EDTA] were unsuccessful. The bacteriocinogenic determinants in the staphylococcal isolates were cured by heating [44°C] and ethidium bromide [300 micro g/mL], suggestive of their plasmid- borne location